Possibility of drift-cyclotron instabilities on the boundary of the polar cusp
It is stated that interaction between the solar wind plasma and the earth's geomagnetic field produces two neutral regions on the noon-midnight meridian, one in the northern hemisphere and the other in the southem hemisphere. These neutral regions are referred to as polar cusps or clefts. The boundary of a polar cusp is a particularly interesting region because of the great variety of plasma instabilities excited there and because of the roles these play in auroral phenomena. The possibility of drift-cyc1otron instabilities on the boundary of the polar cusp is discussed. Evidence supporting direct penetration of solar wind plasma into the polar ionosphere is first reviewed, including satellite observations. Expressions are given for the finite beta driftcyclotron instabilities in an inhomogeneous plasma, together with local dispersion relations for nonresonart and ion-resonant drift-cyc1otron modes. Instability growth rrtes, with possible values of non-dimensional diamagnetic drift velocities on the boundary of the polar cusp, are shown graphically, and approximate maximum instability growth rates and most unstable wave numbers for the possible values of nondimensional diamagnetic drift velocities on the boundary of the polar cusp are shown tabulated. It cannot be said at present what instabilities may be responsible for the disturbances observed by satellites, but drift-cyclotron instabilities are certainly candidates. (UK)
- Research Organization:
- Univ. of British Columbia, Vancouver
- NSA Number:
- NSA-29-022106
- OSTI ID:
- 4347077
- Journal Information:
- Nature (London) Phys. Sci., v. 246, no. 155, pp. 117-118, Journal Name: Nature (London) Phys. Sci., v. 246, no. 155, pp. 117-118; ISSN NPSCA
- Country of Publication:
- United Kingdom
- Language:
- English
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Related Subjects
AURORAE
AURORAL ZONES
BOUNDARY CONDITIONS
CYCLOTRON INSTABILITY
DIAGRAMS
DISPERSION RELATIONS
DRIFT INSTABILITY
EARTH PLANET
GEOMAGNETIC FIELD
INHOMOGENEOUS PLASMA
INSTABILITY
IONOSPHERE
IONS
N56400 --Physics (Astrophysics & Cosmology)--Solar Phenomena
N58100* --Physics (Atmospheric)--Auroral & Ionospheric Phenomena
PLASMA
RESONANCE
SOLAR WIND
TABLES
VELOCITY